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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 8 February 2018 by John Abraham

As humans continue to emit greenhouse gases like carbon dioxide, the world continues to warm. We see that warming everywhere – in the atmosphere, in the oceans, with rising sea levels, and melting ice. But while we know conclusively that humans are causing the warming, an equally important question is, “so what?” Really, we want to know the consequences of warming so that we can make informed decisions about what to do about it. We really have only three choices: mitigate, adapt, or ignore and suffer the consequences.

A very new study was just published that helps answer this question of “so what?” The research was conducted by lead author Lorenzo Alfieri (European Commission – Joint Research Centre, Italy), Richard Betts (University of Exeter and Met Office, UK), and their colleagues.

In the study, the authors used what are called Impact Models to assess the risks of large-scale flooding. They focused their attention on Europe partly because there is a lot of hydrological information there, flood reporting is easily available, and predictions of future climate there are plentiful. The authors compared estimates of flood risk in Europe from three recent case studies; their comparison incorporated changes to future climate, expected damage, and population that will be affected in the flooding zones.

I think of this as a three-part study. First, the authors obtained climate projections for Europe using state-of-the-art climate models. Next, they input the future climate into calculations that quantify flood risk and the impacts. Last, they compared the results that they obtained from their different damage calculation algorithms. The authors looked for areas where the calculations agreed or disagreed with each other. At the end of the day, they wanted to answer two key questions:

1. Is it possible to identify trends that are consistent among the models to help Europe prepare for changes to flood risk?

2. Are there differences in the models and if so, why?

I communicated with Professor Betts who told me:

Our results give the clearest picture yet of climate change increasing the risk of flooding. We did two new sets of model calculations and compared them with a third set from previous work. With all three methods, the result is higher flood risk in Western and Central Europe under a warmer climate, even at just 1.5 degrees C global warming.

Lead author Lorenzo added,

In support to Richard’s statements, the strength of our results comes from the variety of climate projections, methods and models included in this comparison work. The three studies we have considered cover a wide range of variability in projections of flood impacts, thanks to the use of 11 independent climate scenarios, 11 hydrological models, 3 inundation models and 2 impact models. Nevertheless, they all agree on a significant increase in flood risk in most European countries, at all global warming levels.

So where did the models agree and where did they disagree? The answer is shown in the figure below from the paper. Red colors signify agreement between the models on an increasing flood risk, and green indicates agreement on a reduction of flood risk. Light colors and white indicate disagreement on future projections. The left-most column corresponds to temperature increases of 1.5°C, the middle column is for 2°C temperature increases, and the right is for 3°C increases. In summary, the models all agree that flood risk is increasing and will increase for Western and Central Europe.

Comments

The total cost of climate change through flooding, crop damage, sea level rise, and extreme weather, etcetera combined are estimated to cost 12 trillion dollars per year globally by 2050, from an article in the Independent. I understand elevated temperatures will last roughly 1000 years or more, so these are large ongoing costs.

The costs of converting the entire world to renewable electricity are estimated by Jacobson as 5 trillion dollars per year globally, over 20 years. However I would say the amortised cost over a thousand years is more pertinent, and clearly less than one trillion dollars per year. The costs of reducing industrial and agricultural emissions, creating carbon sinks and burying carbon is unknown to me, but I hazard a guess it’s a couple of trillion dollars a year.

To put this in context, global gdp is approximately 100 trillion dollars per year.

So the costs of climate change are 12 trillion per year and the costs of mitigation are perhaps 3 trillion. That’s before one considers human costs, hidden costs, species loss and possible abrupt climate change. It seems the costs of climate change outweigh the costs of mitigation.

This is just my very rough guesstimate simplified calculation, does anyone have a link to a formal up to date study?

For most of Europe by 2050 the risk of drowning appears to be greater than the prospect of dying from heat stroke.

Hansen et al 2016, predict that much of north-west Europe will cool as a result of disruption of the north Atlantic overturning current, caused by discharge of cold water from melting of the Greenland Ice Sheet.

What is not clear from the article is the likely cause of likely flooding in Europe. Will it be due to increased precipitation or sea level rise. Surely not the latter? After all, the IPCC’s 5AR makes it clear that the SLR will be less than I meter by 2100.

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Moderator Response:

[PS] A glance at the title of paper referenced by the article ("Multi-Model Projections of River Flood Risk in Europe under Global Warming") says it river flood risk. I also hope I have linked the correct paper to your Hansen 2016 ref- please learn how to do it yourself.

For most of Europe by 2050 the risk of drowning appears to be greater than the prospect of dying from heat stroke.

Hansen et al 2016, predict that much of north-west Europe will cool as a result of disruption of the north Atlantic overturning current, caused by discharge of cold water from melting of the Greenland Ice Sheet.

What is not clear from the article is the likely cause of likely flooding in Europe. Will it be due to increased precipitation or sea level rise. Surely not the latter? After all, the IPCC’s 5AR makes it clear that the SLR will be less than I meter by 2100.

When you're living in Europe you have realised for long that these 'once in a century' floods are occurring all couple of years now. In Germany that karaokee started already in the late 90s. Ireland is experiencing these events since last decade. And just take a look at France these days.

You only need to open your eyes. Climate change is no more an issue of the future. Climate change is occurring here and now! And this seems to be just a starter...

Thank you Sir Charles for speaking sense. One of the most significant risks associated with AGW is the increased frequency and severity of extreme weather events and it's already been happening. It is not only visible in Europe. The US incurred 306 Billion dollars of damage from extreme events in 2017. What used to be 500 years events happen now on a regular basis. The cost/benefit analysis of not doing anything about climate change does not hold water for second, even from a purely short sighted capitalistic point of view.

@nigelj, I really enjoyed your “rough guesstimate simplified calculation,” for it was very helpful to understand the weight of climate costs through your comparison of these costs to global GDP. As climate patterns continue to become more obscure, I reckon we will see even greater costs associated with the inevitably stronger and more frequent storms, droughts, spurts of desertification, ocean acidification and warming, and increased habitat loss. We are at a pivotal point where turning to mitigation strategies appears like an appropriate next step, but it may not be enough, and to your point, climate change costs certainly outweigh those associated with mitigation. According to 350.org/science, 80% of our planet’s fossil fuel reserves must stay in the ground in order for us to stay below two degrees Celsius of warming. In order for this to occur, the shift to renewable energy must be of utmost priority for nations around the globe, notably the most industrialized and populated. While mitigation techniques offer quick, temporary relief, they are still acting upon the fundamentally destructive, problematic system we have in place. I believe that we must work to absolutely transform the structure of our society from one of capitalist industry to that characterized by virtues of ecological reciprocity and stewardship, if we wish for real change to occur!

I didn’t cite Hansen et al estimate of SLR but rather their prediction of cooling in NW and central Europe. But since you mention it, when it comes to a choice between Hansen et al and 5AR, Hansen gets my vote every time.

River flooding can be caused by SLR, glacier melt or precipitation. By 2100 it seems likely that SLR and precipitation will be the main culprits since ice mass loss from glaciers might be expected to slow due to cooling predicted by Hansen.

The problem I have with the 5AR prediction is that it is widely accepted by Local, State and Federal Governments as the basis on which they zone land and permit building. The result is likely to be that, within 100 years land and buildings could be under several metres of water, giving rise to the question of public liability.

It also enables Governments to ignore what is likely to prove a very real threat to existing infratsructure on which entire economies - and populations - rely for their survival.

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